A podcast is a series of digital media files (either audio or video)
that are released episodically and downloaded through web syndication.
The mode of delivery is what differentiates podcasts from other ways of
accessing media files over the Internet, such as simple download or
streamed webcasts: special client software applications known as
podcatchers (like iTunes, Zune, Juice, and Winamp) are used to
automatically identify and download new files in the series when they
are released by accessing a centrally-maintained web feed that lists
all files associated with the series. (Wikipedia)
Click on this image to subscribe to the Central Church podcast 